Identification and structure elucidation by NMR spectroscopy of an impurity in flame retardants preparation

Polyamidoamines obtained through the polyaddition of natural alpha-aminoacids to N,N'-methylenebisacrylamide were shown to be remarkably active flame retardants for cotton. The presence of a disulfide linkage together with phosphorus atoms was previously chosen as desirable structural requirements and added to the polymer chain for their flame retardants properties. The conjugation of cystamine with diethyl vinyl phosphonate to obtain the desired monomer is accompanied by the formation of a by-product that must be identified and characterized to optimize the reaction. The ability of nuclear magnetic resonance to detect and quantify the components of a mixture in solution has become increasingly important in the analysis of manufacturing processes. Here, we have used NMR spectroscopy to identify and quantify an impurity in the synthesis of the precursor of a flame retardant without removing the main product from solution. 1D and 2D NMR spectra were used to obtain the identification and full characterization of the molecules and the by-product was identified through the analysis of different nuclei, such as ¹H, ¹³C, ¹⁵N and ³¹P.